Production of isobutane



Patented July 15, 1941 2,249,366 FFlCE 2,249,366 PRODUCTION OF I SOBUTANE' Adrianus Johannes van Peski and (lerardus Hendricus Visser,

Amsterdam,

Netherlands,

assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 9, 1938, Serial 2 Claims.

This invention relates to a process for the production of isobutaneirom normal butane.

Th principal object of the invention is to provide a practical and economical process adapted .to the technical scale conversionof normal butane to the commercially more valuable isobutane.

The process of the invention is of great commercial importance in that it provides a direct method for the production, via isomerization, of isobutane. Isobutane is a valuable base material for the production of isobutene which in turn is a valuable starting material in the production of a wide variety of tertiary base oxyderivatives, and it is of particular value as a starting material in the production of hydrocarbon motor fuels of high anti-knock value. Isobutane per se is a valuable starting material in the production of highly branched chain motor fuels and motor fuel constituents by methods comprising the In the Netherlands August 18,

direct coupling or interpolymerlzation of isobutane with the lower olefines as propene and the butenes.

A preferred mode of executing the process of the invention comprises treating the normal butane, in either the liquid or the gaseous phase,

with a catalyst consisting of or essentially com- C., under such pressures as to ensure the presence of a liquid phase, the partial pressure of the hydrogen chloride in the mixture preferably being at least about three atmospheres.

In accordance with the process of the invention, the treated normal butane is in large part converted to isobutane with substantially no loss of either the treated normal butane or the resultant isobutane due to the occurrence of degradation (decomposition) reactions and other undesirable side reactions such as polymerizat on, etc. The process of the invention is selective asv regards the isomerization reaction; in the presence of the specific catalysts and catalyst compositions specified, and under the specific condition of execution of the process as herein defined. the treated normal butane is isomerized to isobutane to the desired substantial extent while there is substantially no loss of either normal butane or isobutane due to the occurrence of degradation'or polymerization side reactions.

The processmay be applied to pure or sub-. stantially pure normal butane or to normalbutane containing mixtures. For example, suitable starting materials are mixtures comprising, besides a substantial amount of normal butane, one or a plurality of other hydrocarbons which may or may not be capable of isomerization under the conditions of execution of the process, or the treated mixture may comprise normal butane and a substantially inert material, such as nitrogen, in which mixture one or more other hydrocarbons may or may not be present. Thus, it is seen that the invention provides means for converting to isobutane the normal butane content of commercial and other hydrocarbon mixtures such as are obtained from the cracking of higher molecular weight hydrocarbons and hydrocarbon mixtures such as petroleum oils, shale oils, petroleum products, animal and vegetable oils, coal, peat, waxes, etc. Conveniently treated normal butane-containing mixtures are the so-called butane-butene fractions (which contain isobutane as well as normal butane) from which the olefines have preferably been removed. Treatment of such mixtures which 'contain both butanes results in very materially increasing their isobutane content and enhancing their value as raw materials in the production of isobutene by catalytic dehydrogenation of isobutane. Technical butanes such as those containing from about 80% to 98% normal butane and from about 20% to 2% isobutane may be treated inaccordance with the process of the invention and their isobutane content increased to 60% or more 1 without any appreciable loss of butanes due to decomposition, polymerization or other undesirable side reactions.

The process is executed in the presence of an aluminum halide catalyst. Practically suitable catalysts of this group are: aluminum chloride and aluminum bromide. The aluminum halide catalyst may be used alone or in admixture with each other and/or other catalytic as well as non-catalytic materials. For example, one or more suitable halideeatalysts may be mixed with or deposited on filler or supporting materials.

The process of the invention is executed in the presence of a hydrogen halide. Such a halide, or

a mixture'thereof, may be added to the reaction,

mixture in the desired amount in any convenient manner. The hydrogen halides may be supplied to the reaction mixture, for example, by adding thereto, continuously or intermittently, a controlled amount of a compound, such as tertiary butyl chloride and'the like halides, which-will, under the conditions of execution of the process, decompose to yield the desired halide. When operating in the vapor phase, the normal butane material may be bubbled through the tertiary butyl hloride or other volatile, readily decomposable halide prior to its passage into the reaction chamber. supplied to the reaction mixture by adding there- In like manner, water-may .be

to a substance, such as an alcohol, which will decompose to yield water under the operating conditions. Especially when carrying out the reaction with an aluminum chloride catalyst it is of advantage to workin the presence of a hydrogen halide, preferably hydrogen chloride.

When the catalytic material is who used in the solid state, it may be employed in any suitable solid form, such as granules, powder or pellets of desired size, or more preferably deposited on a suitable solid supporting or carrier material in manners customary in the execution of catalytic processes of this type. The desired quantity of the catalytic material, in the desired form, may be packed into'a reaction tube, vessel or tower of the desired size and maintained at the desired temperature by suitable heating 'and/or cooling means while the material to be treated is passed into contact with it under the desiredpressure for the desired period of time.

When executing the process with the normal butane in the liquid phase, the catalyst may be employed in either the solid or liquid state, as desired. For example, if it is desired to operate with the catalyst as well as the treated butane material in the liquid phase, one may select a catalyst which is soluble to the desired extent in the liquid normal butane or normal butanecontaining mixture under the conditions of operation. In this manner, intimate contact of the liquid butane and the catalyst is insured. Aluminum bromide is a representative example of a suitable catalyst which is sufliciently soluble in than about 120 (3., because at higher temperatures losses of material due to decomposition and polymerization may be prohibitive. A convenient vapor phase operating range is from about 100? C. to about 120 C. The vapor phase operation may also be executed at temperatures below 100' C.

When the process is executed with the treated butane in the liquid phase, it is desirable to em ploy temperatures not greater than 100 C. In this mode of operation, temperatures higher than 100 C. are unnecessary and are undesirable due to the higher operating pressures and more expensive equipment necessitated. At temperatures below 100 0., the isomerimtion reaction takes place at a practical rate and to a practical extent with substantially no degradation or polymerization of the butane.

According to a preferred embodiment of the process of the invention the-normal butane. is treated with an aluminum halide. preferably aluminum-chloride or bromide, in the presence of hydrogen chloride, at temperatures below about 110 C, under such pressures as to ensure the presence 'of a liquid phase. The hydrogen chloride should preferably bepresent in such a quantity. that its partial pressure will at least be about 3 atmospheres, it having been found that elevated hydrogen chloride pressures are con,- ducive to obtaining higher yields of isobutane With increasing temperature the reaction time necessary for attaining a certain conversion becomes shorter. The preferred temperature range allowing 'of the attainment of a satisfactory conversion within a few hours lies between about 60 and 100 C. i

p A particular advantage of this special mode of executing the process of the invention is that the catalyst retains its activity for a considerable intermittent or' continuous reactor of the auto-,

clave type which is preferably equipped with suitable heating and cooling means and means for agitating the reaction mixture as by mechanical stirring or other suitable methods. The 150- butane may, for. example, be removed continuously or intermittently from the reaction mixture by raising the temperature and/or reducing the pressure, the efliuent material being discharged into a suitable still wherein the isobutane is separated from the normal butane by distillation, and the latter returned to the-reactor. If desired, the formed isobutane may be separated from the unconvertednormal butane by selective absorption or by selective reaction, for example, catalytic dehydrogenation. When the process is executed in the vapor phase with a solid catalyst it is advantageous to apply superatmospheric pressures, e. g. pressures of 10 to 20 atmospheres or higher, since catalyst losses, which are liable to occur as a result of sublimation of the metal halide at elevated temperatures, are thus prea favourable eifect on the isomerisation reaction.

The lowest temperature at which it 'is still possible to work in the vapor phase depends on the pressure applied. Thus, for example, at a pressure of about 10 atmospheres this lowest temperature is about 70 C.

The process, in either the liquid or vapor phase, may be successfully executed over a wide range of contact times of the treated material with' the catalyst under reaction conditions. The most suitable contact time will "depend upon the particular catalyst, the particular reaction conditions such as temperature and pressure, and, when a' normal butane-containing mixture is treated, upon the nature and composition oif such mixture. In any case, the contact time is so chosen with respect to other factors so that the decomposition and/or cracking of the treated and resultant butane is substantially obviated. When operating in the vapor-phase at temperatures of about 0., contact times of from about 10 to about 60 seconds may, in general, be suitable.

The following examples illustrate suitable modes of executing the process of the invention. The invention is not to be regarded as restricted to the particular catalysts, the particular methods of operation, or the particular operating conditions specified in the examples.

Example I A mixture of '76 parts'by weight of a normal butane-containing mixture (89% by weight normal butane and 11% by weight isobutane), 88 parts by weight freshly sublimated aluminum bromide and 7 parts by weight of hydrogen chlo- .ride were heated at 80 C. during 4 hours in a rotating autoclave. The partial pressure of the hydrogen chloride in the mixture at 20 C. amounted to about 3 atmospheres. After re- .moval of the, hydrogen chloride and the alumi- Example II Into one liter ViA-steel autoclave 75 grams of amixture of. 89% by. weight normal butane and 11% by weight of isobutane and 37 grams freshly su'blimated aluminum chloride were introduced, after which an amount of hydrogen chloride was added under pressure. During the reaction the autoclave was rotated.

In the table below the results of operating at various temperatures, with various amounts of added hydrogen chloride and various reaction times are given:

Percent by Partial Percent Reaction pressure a gi g ggggfig' non-C4 temp. in C. rams HCl at 20 hours reaction hydro- 1 g C. in atm. mix'tum carbons 8 4 4 15. 0 8 4 16 16. 8 U 3 4 G4 21. 3 0 4O 20 16 22. 3 0 8 4 4 17. 6 0 8 4 4 22. 2 0 8 4 16 51. 2 0 8 4 2 23. 0 s 4 4 2s. 5 .0 8 4 8 41. 0 0 8 4 18 51. 0 0 18 8 4. 4?- 5 0 36 17 4 46. 0 0 8 4 4 35. 0 0 8 4 4 62 7 0 8 4 4 62 9 7. 7 s 4 4 ,16.7 73.3

While we have described our invention in a detailed manner and'provided specific examples illustrating suitable modes of executing the same, it is to be understood that. modifications may be made and that no limitations other than .those imposed by the scope of the appended claims are intended. We claim as our invention:

1. A process for the isomerization of normal butane to isobutane which comprises contacting normal butane with an aluminum halide catalyst in the presence of at least three atmospheres pressure of a hydrogen halide at a temperature above about C. but below C.' when vapor phase isomerization is carried out, with a contact time not exceeding twenty-four hours, said contact time being of short duration when the decomposition tendency of the hydrogen halide is pronounced under the operating conditions -f or'longer periods, whereby degradation reactions are substantially obviated while the promoter action of the hydrogen halide is retained.

2. A process for the isomerization of normal butane-t0 isobutane which comprises contacting normal butane with an aluminum chloride cataabove about 60 C. but below 120 C. when vapor phase isomerization is carried out, with a contact time not exceeding twenty-four hours, said contact time being of short duration when the decomposition tendency of the hydrogen halide is pronounced under the operating conditions for longerperiods, whereby degradation reactions are substantially obviated while the promoter action of the hydrogen halide is retained.

ADRIANUS JOHANNES- VAN PESI KI. GERARDUS HENDRICUS VISSER. 

